Big teams having separate teams is not a surprise. That doesn't mean they aren't capable doing other tasks at all, where they end up is up to the management obviously. I quickly checked and spotted a job offer from PD (from a while ago) at their site for a CG artist. It mentioned both, car and course modelling amongst other things...
A complete newcomer trying to follow YT tutorials step by step has nothing to do with this.
They have, like, apprentices who do touch up and prep work here and there, mostly props etc. until they figure their specialism. The job vacancy is unlikely to be just one position, PD have form in that regard.
The tools are not the same, PD make their own (well a Sony subsidiary makes them for them), the workflows and data input are subtly different, although not entirely. The cars are semi-parameterised from point clouds and rely heavily on materials shaders, plus they require a lot of rigging; the tracks are standard geometry filtered from point clouds (track surface) and photographs (surroundings), are heavily texture-dependent and require careful attention to lighting and shadow (maps - more textures). Then there are the scapes. Populating the courses / environments with props is a generic job that any modeler could do, but that's a tiny fraction of the total work required.
At the end of the day, it's an efficiency thing. Even in the amateur modding world, people have their specialisations, both in terms of content type and the games they produce for - why? Because it means they can maximise the quality of their work for the time spent.
But take a look at the credits from previous games and you'll see the same names credited to the same things, and a change in structure (implies a change in management paradigm, probably to accommodate team sizes swelling) from GT6.
